From the article:
Bill R, a friend Harry met in Cairns before the war and again at Hamel, says “The shelling was murderous and Harry caught a piece on his head. I (Bill R) ran to him and saw he was in a mortal way and called for an ambulance bearer.
Dalziel’s helmet was thrown onto the rim of a trench with a hole in it a man could put his fist into.
A plate was inserted into Dalziel’s head but he was in and out of hospital the rest of his life.”
Dad didn’t continue to use the plate. It caused problems, probably more headaches. He had an open wound. His brain was visible under layers of skin.
There are other versions of what happened when he was shot in the head. Bill’s account makes sense.